EFFECT OF DELEQUAMINE (RS15385) ON FEMALE SEXUAL-BEHAVIOR IN THE RAT

The role of alpha(2)-adrenoceptors in mediating the noradrenergic cont rol of female sexual behaviour was investigated employing a selective alpha(2)-adrenoceptor antagonist, delequamine (RS15385). The drug was given in graded doses of 0.01-30 mg/kg p.o. to ovariectomised plus adr enalectomised rats primed with either 2 mu g oestradiol benzoate which yielded mainly non-receptive animals or 5 mu g oestradiol benzoate fo llowed 48 h later by 0.5 mg progesterone, which stimulated a high leve l of receptivity. Doses between 0.1 and 30 mg/kg significantly increas ed lordotic activity (receptivity) with an ED(50) of 0.32 mg/kg, but h ad no effect on ear-wiggling or hopping-and-darting (proceptivity). De lequamine had no inhibitory effect in animals displaying high levels o f receptivity. Thus we have shown a selective alpha(2)-adrenoceptor an tagonist, given orally, can stimulate female receptivity in a dose-dep endent manner. Bilateral administration into the ventromedial nucleus, but not medial preoptic area, of delequamine (10 mu g/side/rat) stimu lated receptivity and it is suggested that the alpha(2)-adrenoceptor m ay exert its effect by enhancing endogenous noradrenaline release at i ts active sites.